<template>
  <div>
    <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
       <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
    <div class="header-fixed" 
      v-show="!showAbs"
      :style="opacityStyle"
    >
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      {{sightName}}
    </div>  
  </div>
</template>
<script>

export default {
  name: 'DetailHeader',
  props: ["sightName"],
  data () {
      return {
          showAbs: true,
          opacityStyle: {
              opacity: 0
          }
      }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if(top > 60 ) {
        let opacity = top / 140;
        opacity = opacity > 1 ? 1 : opacity;
        this.opacityStyle = { opacity }
        this.showAbs = false
      } else { 
        this.showAbs = true
      }
    }
  },
  mounted () {
    window.addEventListener('scroll', this.handleScroll)
  },
  destroyed () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
  @import '~styles/varibles.styl' 
  .header-abs
    position: absolute
    left: .2rem
    top: .2rem
    width: .8rem
    height: .8rem
    line-height: .8rem
    text-align: center
    border-radius: .4rem
    background: rgba(0, 0, 0, .8)
    .header-abs-back
      color: #ffffff
      font-size: .4rem
  .header-fixed
    position: fixed
    top: 0
    right: 0
    left: 0
    overflow: hidden
    height: $headerHeight
    line-height: $headerHeight
    text-align: center
    color: #ffffff
    background: $bgColor
    font-size: .32rem
    z-index: 2
    .header-fixed-back
      position: absolute
      top:0
      left:0
      width: .64rem
      text-align: center
      font-size: .3rem
      color: #ffffff
</style>
